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The Biomechanical Model for Minimum Movement Time during Running Walking and Road Cycling 07: The Joint Torque Principle

by Dr. James Kao

 The sixth fundamental Biomechanical principle included in this model is the Joint Torque Principle.  This principle states that an increase in joint torque (TJ) is caused by an increase in a muscle force (FM) pulling on the bones that are held together at the joint and/or an increase in the moment arm (dMA) (i.e., the linear distance from the joint’s axis of rotation to the line of pull of the muscle force).  The line of pull of the muscle force is determined by connecting a line between the attachments (origin and insertion) of the muscle.The equation for the Joint Torque Principle is given here.
Joint Torque Principle Equation

A graphical representation the Joint Torque Principle is presented here.
Joint Torque Principle

 

 

 

 

 

To create a larger muscle force, three factors that influence the size of the muscle force must be considered.

  • The first factor is muscle size.  A muscle with a larger physiological cross-sectional area will create more muscle force.  The method to increase physiological cross-sectional area is resistance training.
  • The second factor is muscle length.  All muscles have a natural resting length.  This natural resting length is found when the muscle is relaxed.  Muscles that are stretched to approximately 120% of their natural resting lengths generate the most muscle force.
  • The third factor is the speed of the muscle contraction.  Muscles that are concentrically contracted at slower speeds generate greater muscle force than muscles that are concentrically contracted at faster speeds.

The moment arm is the distance from joint’s axis of rotation to the line of pull of the muscle force.  If the moment arm distance is increased, the size of the joint torque will increase.

  • To increase the moment arm distance, you would need to move the line of pull of the muscle force further away from the joint’s axis of rotation.  The line of pull of a muscle force is determined by drawing a line connecting the muscle’s origin to it’s insertion. Thus, one method for moving line of pull of the muscle force would be to change the locations of the origin and insertion points for the muscle.  This is not option because it would be unethical to perform this type of surgery.
  • The only way we can change the moment arm distance is by changing the angle of the joint.  When the long axes of the two bones connected at a joint are aligned long axis to long axis (i.e., in a straight line), the moment arm distance is the smallest.  This is because the line of pull of the muscle force passes extremely close to the joint’s axis of rotation.  The maximum moment arm distance is achieved when the long axes of the two bones connected at a joint are perpendicular to each other (i.e., there is a 90 degree angle between the two long axes).  In this joint orientation, the line of pull of the muscle force is the farthest away from the joint’s axis of rotation.

Read more on these topics at Dr. Kao’s blog: http://realworldbiomechanics.blogspot.com/

KIN Alumni Valeri Garcia (Quintero) on Life After Graduation

My name is Valeri Garcia (Quintero).  I graduated from San Jose State University with a degree in Kinesiology with an emphasis in Teaching in 1998.  When I started there, I had wanted to be a college coach and believed that SJSU would give me the best education to become one.  I set out to be a college coach and was able to be one but for only two years.  I turned my attention to college advising but knew, in my heart, that it was youth sports that I would enjoy the most.

During college and after graduation, I continued to coach and help out here and there with several teams but stopped until I had my own kids and it was time for them to play sports.  I now have three amazing, beautiful daughters.  Annelise is 10 years old and Mia and Micaela are 7 (yes, twins!).  I’m a youth sports coach in multiple sports, mostly softball.  Recently, I was awarded the Positive Coaching Alliance’s Double-Goal Coaching award.  At a banquet last week, I was given the opportunity to speak and when I did, I made sure to speak about how wonderful and amazing the faculty and my department was at SJSU and how much I learned from them.  I’ve been asked how I know how to coach and I tell them that I have had great coaches to learn from but I was extremely lucky to have had professionals in the field to teach me through my major.  Though I’m not coaching as a career, I do utilize many ideas that I learned as a student into my job as a college advisor at UC Davis for a program called Guardian Scholars.  We provide support to students that are former foster youth.

It’s long overdue but I want to extend my gratitude for the faculty and education I received from all of you.  I recognize many names from the website that are still teaching that were my professors when I attended.  I’m so glad to know that SJSU’s Kinesiology department continues to have the BEST faculty.

Here is an article in the SacBee that came out today about youth sports.  I was mentioned but, again, I don’t know if i could have be the coach I am today without all of you.

http://www.sacbee.com/2013/08/27/5683034/bruce-maiman-positive-coaching.html

Valeri Garcia (Quintero)
Class of 1998

A Blog Inspired By and Dedicated to Runners

 

by Joshua J. Stone, MA, ATC, NASM-CPT, CES, PES, FNS

I have been looking for something to blog. No idea surfaced that said, “Yes, that is a great blog idea.” That was until yesterday’s tragic Boston Marathon bombing. Runners are a rare breed. You cannot keep them down. A runner’s passion for sport, resilience to challenge, and unique characteristic to rise above is unparalleled by any other athlete. I am not a runner. In fact I am the antithesis of a runner. I go in to anaphylactic shock just hearing the word aerobic exercise, but have many friends who are passionate runners. I dedicate this blog to my running friends, competitors of the Boston Marathon, the friends and family of those impacted by yesterday’s events, and runners everywhere from the competitive to non-competitive. I will keep it true to my blog site and remain sports medicine focused. I hope you find the information useful.

Running is one of the most popular recreational sports in the US. Race events can be found in almost every town. My town – Champaign, IL – has 2 events in the next 4 weeks. Some estimates say 20% of the population is runners and 10% of these people participate in race events. The benefits of exercise are well documented. Running has shown to build confidence and character, reduce stress and improve mood. However, the due to their very nature – the unwillingness stop – running does bring about an increased incidence of musculoskeletal injury.

You don’t need to be an astrophysicist to know running injury is secondary to cumulative overload. Running injuries are multifactorial; neuromuscular imbalance, poor arthrokinematics and other things such as age, nutritional status and environment are to blame. From a biomechanical point of view frontal plane knee adduction moments play a significant role in lower extremity injury. Q-angle – a measure of knee alignment – can indicate risk for running injury. An increased Q-angle can be a result of many neuromusculoskeletal inefficiencies from poor muscular hip control to limited ankle dorsiflexion and excessive forefoot pronation.

Running brings about many injuries, but the most common are Patellofemoral Syndrome, Iliotibial Band Syndrome, Medial Tibial Stress Syndrome / Tibial Stress Fracture, Achilles Tendinitis, Plantar Fasciitis, and Sacroiliac Joint Pain. What is interesting is that all of these injuries can be caused by biomechanical breakdown and neuromusculoskeletal inefficiency. The good is the dysfunctional patterns are identifiable, preventable and correctable. Below is a sample 15 minute injury prevention program from a blog I wrote in Sept 2012. Yes, 15 minutes is all you need to prevent many running injuries.

Step 1: Decrease neurological drive to hypertonic tissue – 3 minutes

  • Self-Myofascial Release (foam roll) or Manual Trigger Point Therapy
    • Gastrocnemius/Soleus – 60 seconds
    • Adductors – 60 sec
    • TFL/IT-band – 60 sec

Step 2: Lengthen hypertonic muscle or joint tissue – 3 minutes

  • Static stretch or joint mobilization
    • Gastrocnemius/Soleus Stretch – 1 set @ 30 sec
    • Kneeling Hip Flexor Stretch – 1 set @ 30 sec
    • Adductor stretch – 1 set @ 30 sec
    • Posterior joint mobilizations at the ankle – 90 seconds

Step 3: Increase neurological drive to hypotonic tissue – ~ 6 minutes:

  • Exercise: Isolated Strengthening or positional isometrics
    • Resisted Ankle Dorsiflexion – 2 sets x 15 reps (slow) (2 minutes)
    • Resisted Hip Abduction and External Rotation- 2 sets x 15 reps (slow) (2 minutes)
    • Resisted Hip Extension – 2 sets x 15 reps (slow) (2 minutes)

Step 4: Integrated Dynamic Functional Movement – ~ 3 minutes

  • Box step-up with overhead dumbbell press – 2 sets x 15 reps (slow)

Beyond the correction of movement dysfunction there are alternatives to treat running injuries which are effective and gaining popularity. This table highlights a few.

Prolotherapy This has been around since the late 1800’s, but has since become popular. The basis of prolotherapy is that it expedites healing by increasing fibroblastic activity and collagen repair.
Autologous Blood Blood is the medium that carries tissue repairing materials to injury sites. However, sometimes, blood cannot deliver adequate amounts of material to the injured area. Thus, injections directed right at the injury site deliver tissue repairing material.
PRP Like autologous blood, Platelet Rich Plasma (PRP) is injection of a concentrated mix of tissue repairing blood components, specifically platelets, which facilitate tissue repair healing.
Bone Marrow Aspirate Concentrate Despite the negative press and belief that stem cells are only derived from an unborn fetus, stem cells do come from other sources – such as bone marrow. By taking stem cells from bone marrow and injecting in to damaged areas will facilitate tissue repair.
ESWT Extracorporeal Shock Wave Therapy might best be known as lithotripsy. Lithotripsy is a procedure in which sound waves blast and destroy kidney stones. ESWT is the use of sound waves to destroy calcific tendons and ligaments.

I prefer preventing and rehabilitating injury through correcting neuromuscular inefficiencies and dysfunctional movement. The problem with the above treatments is that they are treatments. If an injury is caused by dysfunctional movement patterns and those patterns are not corrected it is likely the above treatments will simply serve as a Band-Aid because the true problem was not fixed.

If the person(s) responsible for the Boston Marathon bombing were looking to put fear in people, they chose the wrong population to target. Runners are the most stubborn and prideful athletes. No means yes, and yes means do more. If you took a graphical representation of marathon registration numbers from last night through the end of this week I would bet you’d find a spike, rather than a decline. Social media is exploding with a rise of the runner. A quote from a friends Facebook page: “If you’re trying to defeat the human spirit, marathoners are the wrong group to target” –unknown. Other movements like, wear a race shirt tomorrow, donations, and wear yellow and blue (Boston Marathon colors) have already begun. So, thank you runners for inspiring this blog post!

Find more of Josh’s work here.